I think it is something with how much of the regular flange is threaded. I don’t think you can get the flange tight on a stacked dado. I tried to use the dado nut with a single blade, and it wouldn’t thread on all the way.

I’ve never even heard of a “dado nut” for the Uni. I run a stacked dado all the time with just the nut, on the wider cuts there is no room for the flange washer….......maybe that’s why they want to pick your pockets.